There is this third party user script you can install that might help:
Lesson Lock by @Kumirei: Displays 0 lessons when you have too much on your plate already. Completely customisable to lock lessons when you have anything between 1 apprentice1 items or a million enlightened items.
This next link goes to directions on how to install userscripts in general:
https://community.wanikani.com/t/visual-guide-on-how-to-install-a-userscript/